1. Technical Field
The present invention relates to a positioning satellite signal receiving method etc.
2. Related Art
Positioning satellite signal receivers represented by GPS (Global Positioning System) receivers have been widely spread. The GPS receiver captures a plurality of GPS satellite signals, performs position calculation using navigation messages superimposed and carried on the respective captured GPS satellite signals, and thereby, obtains a position and a clock error (clock bias) of the GPS receiver. There are many requests for the GPS receiver, and particularly, a representative request for the GPS receiver mounted on a portable electronic apparatus is to reduce power consumption. In order to respond to the request, for example, JP-A-2011-220998 discloses a technology of reducing power consumption by reducing an amount of correlation calculation between received signals and replica codes.
The above described technology of JP-A-2011-220998 reduces the power consumption by sampling the received signals at a sampling rate of an integer multiple of a chip rate of C/A (Coarse and Acquisition) codes as spread codes of the GPS satellite signals and performing correlation calculation. However, with the sampling rate of the integer multiple, there is a tendency that the peak of the calculation result of the correlation calculation is broader compared to the case where the received signals are sampled at a sampling rate of a non-integer multiple of the chip rate of C/A codes because the sampling numbers are equal among the respective chips of C/A codes. As a result, accuracy of acquired measurement data may be lower.
In the GPS receiver, first, the GPS satellite signals are acquired, and then, the position calculation is performed using the measurement data (reception frequency and code phase) acquired from the tracked GPS satellite signals. The accuracy of the position calculation depends on the accuracy of the measurement data (reception frequency and code phase) for use.